Electrical terminal



Oct. 15, 1935. 1 H FlSHER Er AL 21,017,204 Y ELECTRICAL TERMINAL Filed March 8, 1932 ATTORNEYS Patented Oct. 15, 1935 UNITED STATES PATENT OFFICE 1 assignors to Aerovox Corporation,

Brooklyn, N. Y., a corporation of New York Application March 8, 1932, Serial No'. 597,478

7 Claims.

Our present invention is concerned in general with the provision of a mechanically secure, electrically perfect and liquid-tight electric terminal connection. Such terminals have manifold uses. They are particularly desirable in connection with oil filled electric condensers where the principal problem involved is to prevent leak of oil around the terminal members during the storage, transport or use of the instruments.

An object of the invention is to provide a terminal structure of this character which will be entirely proof against leak thereabout even at high temperatures and regardless of Whether or not the oil lled condenser casing is accidentally inverted or tipped on its side during transport or storage or use.

Another object is to provide a terminal construction which will permit the terminal assemblage to be completed in far less time than is now possible and a terminal which will not only be tighter but stronger than those heretofore used. i

Another object is to provide a terminal structure which automatically compensates for the expansion of certain of the metal terminal parts under the influence of heat and particularly accommodates for such expansion at the temperatures at which said condensers are most often used, say at or above F.

Another object is to provide a terminal structure in which a molded seal about the terminal is effected as an incident of assembling and securing the terminal and without the use of any special treatment or special application of heat.

It has heretofore been customary to use screws and nuts together with suitable washer assemblages to serve as the terminals of oil filled electrical condensers. Regardless of the tightness with which the condenser casings themselves may be sealed, the oil has tended to leak out around the terminals by following the screw threads eS- pecially during expansion of the metal parts at high temperatures.

By our present invention we provide a strongen simpler, leak-proof terminal arrangement n which a threadless member such as a rivet is employed, the rivet being capable of effecting a tighter clamping of the washers. Preferably also the assemblage includes a pair of overlying Bakelite washers, the riveting operation tending to weld these washers together and cause them to flow about the rivet and form a molded insulating seal. Furthermore by supplementing the Bakelite washers with brass or aluminum washers and by using a steel rivet, the expansion of the steel at the operating temperatures of the condenser is counteracted by the greater expansion of the brass or aluminum with the result that at operating temperatures an entirely satisfactory seal is maintained.

The invention may be more fully understood from the following description in connection with the accompanying drawing wherein:-

Fig. 1 is a diagrammatic view partly in side elevation and partly in vertical section through a condenser equipped with our improved terminal structures,

Fig. 2 is an enlarged vertical sectional view through one of the terminals and Fig. 3 is a top plan view of one of the terminals.

In the drawing the condenser casing consists of a metallic can or box I0 provided with a-cover II, the latter being beadedover and soldered to the can as at I2. Preferably the terminal structures indicated generally at T are applied to the can top, insulated therefrom and are electrically connected to the condenser leads I3 andl I4 prior to the final application and sealing of the top to the can.

Insofar as the condenser structure itself is concerned the condenser C may be of any conventional character, typically a heavy duty condenser substantially submerged in a bath of oil.

In Fig. 2 we have illustrated the manner in Which the terminal members are applied to the can top I I. The can top is provided with an opening I5 thereinv of considerably larger diameter than the rivet I6 which holds the various washers and connector members of the terminal structure together. A pair of insulating washers I'I (preferably of the phenolic condensation product known as Bakelite or some equivalent material subjectto flow under heat and pressure) are arranged on opposite sides of the condenser top, these washers being of appreciably larger size than the opening I5. Above the upper Bakelite Washer I'I there is a washer I8 of brass or aluminum and below the lower Bakelite washer I1 there is a second washer I9 of brass or aluminum. All of the Washers have aligned central openings as does the outer terminal piece I9 and the inner terminal piece 20.

The inner terminal piece may consist simply of an eyelet or apertured lug 2I having a terminal end 20 for attachment to the lead wire I3 or I4 as the case may be. The outer terminal piece I9 also consists of a lug 22 having integral therewith an upwardly and laterally extending arm 23 from which are bent suitable ears `24 and 25 to engage and clamp or be soldered to an external lead wire (not shown).

The rivet which is originally provided with only one head 26 is assembled, together with the various washers and terminal pieces, and the riveting operation is performed in a Grant riveting machine or some equivalent apparatus to spin rather than hammer over the other rivet head 2l.

As a result of this riveting operation Bakelite Washers I'I are caused to flow together to the extent indicated by the pressure (and the heat generated by such pressure) of the brass washers which back them. They completely lill the opening I5 of the can top and they are caused to very tightly embrace the shank of the rivet I6. Thus the two washers become joined by a bridge of length equal to the thickness of the can top or other support plate. The two washers with their connecting bridge thus form an integral bushing of homogeneous texture throughout, not subject to the difiiculties of a composite bushing of two separate parts pasted together. By the use of this rivet we not only are able to effect a better and sturdier connection between the various parts of the terminal assembly but we are able to apply any desired pressure so that the washers and terminals are riveted together with exceeding tightness.

Under the temperatures encountered during normal operation of the condenser, the steel rivet I6 will expand to a lesser extent than will the brass washers IB with the result that the seal between the steel rivet and brass washers is always maintained tight.

We prefer to use a Grant riveter or some other machine which spins the head of the rivet over rather than hammers it since this mode of operation minimizes the danger of cracking the washers or the terminal members and the pressure induced heat is sufficient to impart the desired internal flow to the Bakelite washers.

The terminal structures on the can top having been assembled, and the terminals 20 attached to the lead wires I3 and I4 by soldering or otherwise, the top Il is sealed in position and an entirely liquid tight condenser casing is formed requiring no special care in transport or storage and capable of being used on its side or even in inverted position if desired, without danger of oil leak.

It will thus be seen that there is herein de'- scribed apparatus in which the several features of this invention are embodied, and which apparatus in its action attains the various objects of the invention and is well suited to meet the requirements of practical use.

As many changes could be made in the above construction, and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not In a limiting sense.

Having thus described our invention, what we claim as new and desire to secure by Letters Patent iszy 1. A method of forming a liquid-tight electrical terminal which includes the steps of disposing at opposite sides of an opening in a container, insulating washers of the character subject to ux and weld under pressure, backing said washers with pressure applying washers and riveting all of said washers together with a rivet having a shank of less diameter than the opening in the container and passed through said washers and applying sufficient force to the rivet to induce the flow of the material of the insulating washers into the space between the rivet shank and the wall of said opening. f

2. A method of forming a liquid-tight electrica terminal which includes the steps of disposing at opposite sides of an opening in a container, insubushing.

lating washers of molded material, backing said washers with pressure applying washers and riveting all of said washers together with a rivet having a shank of less diameter than and passed through the washers and through the opening in 5 the container and applied with sufficient force to induce the flow of the material of the insulating Washers to weld together into an integral structure substantially filling the space between the rivet shank and the wall of said opening. 10

3. An electrical terminal mount of the class described, including a thin supporting plate, rigid washers of insulating material resting against opposite faces of said plate, said washers having a connecting neck constituting a short bridge intel5 gral and homogeneous in texture with both said Washers and snugly lining an aperture through said plate, and a rivet through said aperture and through said washers maintaining the latter securely pressed against said plate.

4. An electrical terminal mount of the class described, comprising a thin metal apertured supporting plate, a rigid insulating bushing therethrough, comprising a pair of insulating washers having a short connecting bridge integral with 25 both said washers, of a height equal to the thickness of said plate and snugly lining the aperture in said plate, and a solid metal rivet through said bushing having heads exerting pressure against said Washers and said connecting bridge, said rivet 30 having a shank snugly fitting within said bushing.

5. An electrical terminal mount of the class described, comprising a thin metal apertured supporting plate, a rigid insulating bushing there- 35 through, comprising a pair of insulating washers having a short connecting bridge integral with both said washers, of a height equal to the thickness of said plate and snugly lining the aperture in said plate, metal washers of`diameter less than 40 said insulating washers, and a solid rivet bushing snugly fitting the bushing and transmitting pressure through said metal washers against said 6. A liquid-tight electrical terminal mount for electrical instruments of the character housed in liquid containing conductive casings and subject to heating during use, said terminal mount comprising an insulating bushing for an apertured sheet metal wall of said container, said bushing comprising a pair of rigid insulating Washers having integral and homogeneous in texture therewith a short rigid connecting bridge of length equal to the thickness of said sheet metal wall and snugly lining said aperture, a solid rivet through said bushing and snugly fitting the latter. said rivet having heads exerting pressure upon said bushing.

7. A liquid-tight terminal, comprising a support, an insulating bushing therethrough, metal washers at opposite faces of said bushing and of combined thickness substantially equal to the axial length of said bushing, a rivet through said metal Washers and said bushing, said rivet having' heads exerting pressure through said metal wash- 55 ers against said bushing, said metal washers having a coefiicient of expansion greater than that of said rivet, whereby the tightness of' the latter remains intact under expansion when the terminal becomesheated.

JOHN H. FISHER. SAMUEL SIEGEL. 

